71. Simplify Path
Tags: ‘String’, ‘Stack’
Given an absolute path for a file (Unix-style), simplify it. Or in other words, convert it to the canonical path.
In a UNIX-style file system, a period . refers to the current directory. Furthermore, a double period .. moves the directory up a level. For more information, see: Absolute path vs relative path in Linux/Unix
Note that the returned canonical path must always begin with a slash /, and there must be only a single slash / between two directory names. The last directory name (if it exists) must not end with a trailing /. Also, the canonical path must be the shortest string representing the absolute path.
Example 1:
Input: "/home/" Output: "/home" Explanation: Note that there is no trailing slash after the last directory name.
Example 2:
Input: "/../" Output: "/" Explanation: Going one level up from the root directory is a no-op, as the root level is the highest level you can go.
Example 3:
Input: "/home//foo/" Output: "/home/foo" Explanation: In the canonical path, multiple consecutive slashes are replaced by a single one.
Example 4:
Input: "/a/./b/../../c/" Output: "/c"
Example 5:
Input: "/a/../../b/../c//.//" Output: "/c"
Example 6:
Input: "/a//b////c/d//././/.." Output: "/a/b/c"
Solution
Simplified version
40% 86%
public String simplifyPath(String path) {
Deque<String> stack = new LinkedList<>();
Set<String> skip = new HashSet<>(Arrays.asList("..",".",""));
for (String dir : path.split("/")) {
if (dir.equals("..") && !stack.isEmpty()) stack.pop();
else if (!skip.contains(dir)) stack.push(dir);
}
String res = "";
for (String dir : stack) res = "/" + dir + res;
return res.isEmpty() ? "/" : res;
}
5% 100%
public String simplifyPath(String path) {
if (path == null || path.length() == 0) return "/";
StringBuilder sb = new StringBuilder();
Deque<String> stack = new ArrayDeque<>();
String[] array = path.replaceFirst("^/+", "").split("/+"); // split will only remove trailing empty spaces
for (int i = 0; i < array.length; i++) {
String curr = array[i];
if (curr.equals(".")) {
continue;
} else if (curr.equals("..")) {
if (!stack.isEmpty()) stack.pop();
} else {
stack.push(curr);
}
}
// finally build path from stack
Iterator iter = stack.descendingIterator(); // reverse the iterator for Deque
while (iter.hasNext()) {
sb.append("/" + iter.next());
}
if (sb.length() == 0) sb.append("/");
return sb.toString();
}